Gonorrhoeal disease affects over 2 million people per year in the U.S. Controlling this epidemic disease at present is a major problem even though treatment with antibiotics is available and effective. Currently no vaccine has been found to be protective against a wide spectrum of gonococci. Several different antigens are potentially good vaccine candidates such as pili and porins. However, there are others that might potentially be hazardous such as protein 111 and the lipooligosaccharides. The basic aims of this proposal is to understand the basic antigenicity of three proteins i.e. pili, protein I. and protein III. Because the portion on the pilus protein which adheres to human cells is produced during the assembly of this structure from monomers, this process will be examined in detail. Several epitopes available on monomers become concealed during this assembly. Through epitope mapping with monoclonal antibodies to the monomer, these epitopes will be defined. Furthermore, epitopes which remain exposed will also be defined. These same monoclonal antibodies with defined epitopes will be used to understand the binding of this molecule to human cells. The porins, the gonococcal proteins I, are less variable than most other proteins of the organism. Through epitope mapping by monoclonal antibodies raised to different porins, a region of this molecule which is common to all porins will be defined. Also, an area which divides these porins into two major classes will be defined. The monoclonal antibodies to these defined regions will be evaluated as to their bactericidal and opsonic activity. Certain epitopes on protein III evoke antibodies which potentially block the otherwise potent bactericidal antibodies to other antigens on the bacterium. These exposed epitopes will be defined with monoclonal antibodies raised to the purified protein. How these epitopes interact with protein I will be explored.